Laminated easy opening end for cans



June 18, 19 68 E. L. HAZARD LAMINATED EASY OPENING END FOR CANS Filed Sept. 14, 1964 INVENTOR 'ELLlSON L,. HAZARD p Whip MQ M United States Patent 3,388,824 LAMINATED EASY OPENING END FOR CANS Ellison L. Hazard, Darien, Conn, assignor to Continental Can Company, Inc., New York, N.Y., a corporation of New York Filed Sept. 14, 1964, Ser. No. 396,085 13 Claims. (Cl. 220-27) ABSTRACT OF THE DISCLOSURE This invention relates in general to new and useful improvements in cans, and more particularly to a novel end for a can of the easy opening type.

It will be readily apparent that a can end must have sufiicient strength to permit the ready handling of an associated can without the rupture of the can end. Furthermore, when the can end is utilized as a part of a can for beverages and like liquids packed under pressure, the can end must have sufficient strength to prevent the excessive outward bowing thereof. As a result, the thickness of the metal utilized in the forming of can ends is restricted even though it is desirable to reduce the thickness of can ends for economy.

The conventional can end now used for the forming of beverage cans is formed of tinplated steel, which is generally referred to as tinplate, and is generally known in the can making industry as 90#TH tinplate. It has been found that utilizing a conventional puncture-type can opener, the average opening force for such tinplate, which has a thickness of approximately 0.0099 inch, is 14 pounds. This opening force has proven to be too great for many persons. As a result, the manufacturers of beverage cans have been making cans wherein one end thereof is formed of aluminum although the aluminum can ends are more expensive than the tinplate can ends. The conventional aluminum can ends have a thickness of 0.0145 inch and the average opening force for Opening such a can end with a conventional puncture-type can opener is 11 pounds. This opening force has also proved to be too great for many people and this is one of the reasons why many people desire the can ends of the pull tab type despite the fact that such can ends are much more expensive.

In the opening of a solid metal can end, either tinplate or aluminum, the maximum force is required at the time the point of the puncture-type can opener is being forced through the metal. After the initial puncture has occurred, the further rupture of the metal of the can end is of a tearing and bending nature and much less force is required. Further, during the initial puncturing the point of the can opener actually does the cutting of the metal While the can opener behind the point performs a spreading operation. Therefore, the opening force required for a given type of metal is not directly proportional to the thickness thereof. It is upon this principle and others that this invention is based.

In view of the foregoing, it is the primary object of this invention to provide laminated can ends for use in the manufacture of cans adapted to contain liquids and which cans are to be opened by the puncturing of the laminated can ends utilizing a puncture-type can opener, the lami- "Ice nated construction of the can ends providing for the neces sary strength and at the same time reducing the average force required to effect the puncture and opening thereof.

Another object of this invention is to provide a novel can end particularly adapted for cans containing liquids which are to be opened by means of a puncture-type can opener, the can end being of a laminated construction and including two outer metal plies and an intermediate ply which is formed of a softer material than the outer plies whereby in the opening of the can, the exterior metal ply of the can end is first ruptured, followed by a relatively easier movement of the point of the opener through the intermediate ply, after which there is a momentary increase in resistance to movement of the point of the can opener through the can end due to the engagement of the point of the can opener with the interior metal ply, the required opening force at any one time being much less than that for a single thickness of metal having the required strength characteristics.

Still another object of this invention is to provide a novel laminated can end intended for use as a part of a can for liquids which is of the easy opening type, the laminated can end being of a construction whereby the outer plies thereof are formed of metal, and the metal may be either conventional tinplate or conventional aluminum as is presently utilized in the formation of can ends.

Another object of this invention is to provide a threeply laminate can end wherein the two outer plies are formed of metal, and the inner ply is formed of a relatively soft material preferably in the form of a high tensile strength-low shear thermoplastic whereby the force required to open the can end utilizing a conventional puncture-type can opener is greatly reduced as compared to the opening force now required with respect to either tinplate or aluminum can ends.

A further object of this invention is to provide an all metal can end which is of a laminated construction, the can end being formed of two plies of relatively hard and relatively thin tinplate as compa ed to that which is presently utilized in the forming of can ends, and the two piles of tinplate being joined together by an intermediate ply of solder, which solder is, of course, softer than the tinplate plies, the over-all thickness of the can end being similar to that of conventional can ends while the resistance to opening with a conventional puncture-type can opener is less.

With the above and other objects in view that will hereinafter appear, the nature of the invention will be more clearly understood by reference to the following detailed description, the appended claims and the several views illustrated in the accompanying drawings.

In the drawings:

FIGURE 1 is a perspective view of a can formed in accordance with this invention and shows the same being opened by means of a conventional puncture-type can opener which is being utilized to puncture an opening in the top end of the can.

FIGURE 2 is an enlarged fragmentary vertical sectional view taken along the line 2--2 of FIGURE 1 and shows the specific laminated construction of the can end.

FIGURE 3 is an enlarged fragmentary vertical sectional view similar to FIGURE 2 and shows a different type of laminated can end construction.

Referring now to the drawings in detail, it will be seen that there is illustrated in FIGURE 1 a can which is generally referred to by the numeral 5. The can 5 includes a conventional can body 6 which has the lower end thereof closed in a conventional manner by means of a conventional can end, the lower can end being secured to the can body 6 by means of a conventional double seam 7. The upper end of the can body 6 is closed by a can end 8 which is formed in accordance with this invention. The can end 8 is secured to the upper end of the can body 6 by means of a conventional double seam 9'. The can end 8 is of a conventional configuration and differs from conventional can ends only in that it is of a laminated construction as compared to the single ply construction of conventional can ends. The can ends 8 is formed of an exterior ply 10 of metal which is bonded to an interior ply 11 of metal by means of solder 12. It has been found that when the ply 10 is thicker than the ply 11, the opening force required to puncture the can end 8 utilizing a conventional puncture-type can opener is less. Such a can opener is clearly illustrated in FIG- URE 1 and is referred to by the numeral 13. It will be readily apparent that the can opener 13 is provided with a sharp point and that the nose of the can opener 13 increases in width rearwardly from the point.

It has been found that when the can end is of a single ply construction, the point of the can opener 13 performs a cutting operation as it is forced through the metal of the can end while the nose of the can opener rearwardly of the point must plow through the metal in a wedging manner so as to force the metal apart. It will be readily apparent that inasmuch as the wedging operation increases as the point passes through the metal, the force required to open a single ply can end does not vary directly with thickness, but increases with an increase in thickness.

Referring once again to FIGURE 2, it Will be readily apparent that when the can end 8 is opened with the conventional puncture-type can opener 13, the point of the can opener 13 will initially cut through the metal of the outer ply 10 and as the point of the can opener passes through the metal of the outer ply 10, the nose of the opener will force the metal apart. However, the force required to pass the point of the can opener 13 through a relatively thin ply, such as the exterior ply 10- of the can end 8, is proportionately less than that which will be required for relatively thick metal. After the point of the can opener 13 passes through the exterior ply 10, it comes into engagement with the solder 12. Since the solder 12 is relatively soft, it will be readily apparent that the point of the can opener 13 will easily pass through the solder 12 and therefore while the total thickness of the plies 10 and 12 is greater than the thickness of the ply 10, the force required at the time the point is passing through the solder 12 is less than that required to pass the point of the can opener 13 through the exterior ply 10'.

After the point of the can opener 13 passes through the solder ply 12, it comes into engagement with the interior ply 11. The force required to penetrate the interior ply 11 is greater than that required to penetrate the solder ply 12. However, the force required to wedge the nose of the opener 13 through the solder ply is greatly reduced as compared to that required to force the nose of the opener through solid metal. Also, it has been found that by making the interior ply 11 of a lesser thickness than the exterior ply 10, the force required to pass the point of the can opener 13 through the interior ply 11, despite the fact that the nose of the can opener is being wedged through the plies 10 and 12, is not materially greater than that required to force the point of the can opener through the exterior ply 10 alone. In view of this, although it would not be apparent that an all metal laminated can end could be more easily punctured than a one-piece metal can end, it has been found that the opening force is materially less.

A typical all metal can end which has proved to be successful is one wherein the exterior layer is formed of 40#T8 tinplate having a thickness of approximately 0.0044 inch and an interior ply of #T3 tinplate having a thickness of approximately 0.0039 inch which is bonded together by a solder which is 50% tin and 50% lead. It is to be understood that T8 and T3 are hardness symbols known in the can making industry. Extensive tests have shown that a laminated can end of this construction has the same strength as conventional tinplate and aluminum can ends while the average force required to open the laminated can end is 9.1 pounds, a reduction of 35% in the opening force required for conventional tinplate can ends.

Referring now to FIGURE 3 in particular, it will be seen that there is illustrated a slightly modified form of can end which is referred to by the numeral 14 and is secured to the can body 6 in the same manner as is the can end 8 by means of a conventional double seam 15. The can end 14, like the can end 8, is of a laminated construction and includes an exterior metal ply 16, an intermediate ply 17 and an interior metal ply 18. The intermediate ply 17 is formed of a. high tensile strength, low shear thermoplastic. The thermoplastic material of the intermediate layer 17 is suitably bonded to the metal plies 16 and 18 in a conventional manner which is not a part of this invention.

It has been found that the metal plies 16 and 18 may be formed of either tinplate or aluminum, and that the most suitable thermoplastic materials are polyethylene and polycarbonate although the invention is not restricted to either of these thermoplastic materials nor to tinplate and aluminum.

The following is typical of the metal-thermoplastic material-metal laminates which have been tested and which proved successful for the forming of can ends, and the average opening force required to open such can ends:

It will be readily apparent from the foregoing table that an amazing result can be obtained when a laminated can end is utilized, particularly wherein the intermediate ply is formed of a thermoplastic material which is relatively soft and at the same time has a high enough tensile strength so as to possess the necessary characteristics for the forming of a strong can end.

It is to be understood that the laminated can ends formed in accordance with this invention require no scoring or other means for weakening the same at a desired point of opening, and are in no way limited to the point where the can opener must be applied. It will also be apparent that inasmuch as the exposed plies are formed of metal, there is no problem of sealing and exposure of the product to the metal of the can end which does not normally occur. Furthermore, it will be readily apparent that it is possible to form the exterior layer of a can end of tinplate with the interior layer being formed of aluminum so that the can end may have the beneficial characteristics of aluminum with respect to beer and similar beverages. In addition, inasmuch as the exposed plies are formed of metal, they may be readily decorated or enameled in the same manner as are conventional can ends. At this time it is pointed out that the plies of the metal-thermoplastic material-metal can ends can be bonded together by means of the thermoplastic material directly bonding to the metal or a suitable adhesive may be interposed therebetween.

It is acknowledged that broadly speaking laminates have been utilized in the past in the forming of containers. However, prior to this time, no one has formed a laminated can end which has all of the strength requirements of single ply metal and at the same time provides for an amazing reduction in the opening force required to open the can end with a conventional puncture-type can opener.

Although only several preferred laminates have been specifically disclosed herein, it is to be understood that other laminates could be utilized when formed in accordance with the general spirit of this invention, as defined by the appended claims.

I claim:

1. A can particularly adapted for the packaging of liquid, said can comprising a metal body and closure means at one end of said metal body intended to be opened by a conventional type of combined puncturing and tearing opener from the outside inwardly and being capable of resisting forces normally imposed on can ends in the use thereof, said closure means being in the form of a conventionally shaded can end and being secured to said metal body by means of an upstanding bead, said closure means including an end panel disposed in recessed relation within said seam whereby said seam may function as a fulcrum type support, and said closure means being formed of a laminate of at least three plies including outer metal plies and an intermediate ply bonding together said metal outer plies, said intermediate ply being formed of a material having a lesser resistance to puncture than said metal outer plies whereby in the forming of an opening in said can end there will be a progressive puncturing of the several plies with the several plies ofiering less resistance to puncture than conventional one-piece metal can ends, said metal outer plies being imperforate and free of pre-formed weakening lines.

2. The easy opening can of claim 1 wherein said intermediate ply is formed of metal.

3. The easy opening can of claim 1 wherein said intermediate ply is of a lesser thickness than each of said metal outer plies.

4. The easy opening can of claim 1 wherein said intermediate ply is formed of metal and is of a lesser thickness than each of said metal outer plies.

5. The easy opening can of claim 1 wherein said metal outer plies are formed of tinplate and said intermediate ply is formed of solder.

6. The easy opening can of claim 1 wherein said metal outer plies include an interior metal ply and an exterior metal ply, and said exterior ply is thicker than said interior ply.

7. The easy opening can of claim 1 wherein said intermediate ply is formed of a high tensile strength low shear thermoplastic and said intermediate ply is thicker than both of said outer plies.

8. The easy opening can of claim 1 wherein said intermediate ply is formed of a high tensile strength low shear thermoplastic and said intermediate ply is thicker than both of said outer plies, said intermediate ply having a thickness ranging from 0.006 inch to 0.009 inch and each of said metal outer plies has a thickness ranging from 0.0015 inch to 0.0045 inch.

9. The easy opening can of claim 1 wherein said intermediate ply is formed of a high tensile strength low shear thermoplastic and said intermediate ply is thicker than I both of said outer plies, said intermediate ply being formed of polyethylene and said metal outer plies being formed of tinplate.

10. The easy opening can of claim 1 wherein said intermediate ply is formed of a high tensile strength low shear thermoplastic and said intermediate ply is thicker than both of said outer plies, said intermediate ply being formed of polyethylene and said metal outer plies being formed of aluminum.

11. The easy opening can of claim 1 wherein said intermediate ply is formed of a high tensile strength low shear thermoplastic and said intermediate ply is thicker than both of said outer plies, said intermediate ply being formed of polycarbonate and said metal outer plies being formed of tinplate.

12. The easy opening can of claim 1 wherein the average force required to form an opening in said can end with a conventional puncture-type can opener ranges between 4 pounds and 9.1 pounds.

13. The easy opening can of claim 1 wherein the average force required to form an opening in said can end with a conventional puncture-type can opener ranges between 4 pounds and 5.75 pounds.

References Cited UNITED STATES PATENTS 2,362,893 11/1944 Durst 29-194 X 2,469,416 5/1949 Smyers 161-217 X 3,067,910 12/1962 Adamsen 22054 FOREIGN PATENTS 939,771 10/ 1963 Great Britain.

THERON E. CONDON, Primary Examiner.

JOSEPH R. LECLAIR, GEORGE E. LOWRANCE,

Examiners. 

